1. Field of the Invention
The invention is related to the field of telecommunications, and in particular, to methods and systems for testing a circuit in a communication network.
2. Description of the Prior Art
As is known, telecommunication service providers have created cross country or ultra long haul networks. These networks are driven, in part, by the nature of Internet and data traffic and by ever expansive enterprise networks. Voice traffic, on the other hand, is characterized as more regional and served principally by metropolitan and regional networks. Network planners visually depict these two developing traffic patterns as network overlays, served by different transmission equipment. Internet and data traffic over these networks has been increasing at a significant rate and currently dominates voice traffic for many long distance service providers.
Telecommunication service providers continually look toward new technologies leading to greater network carrying capacity, or bandwidth, and increasing transmission distances, which are the length separations between system transmitting and receiving terminals. DWDM is the favored optical technology for increasing bandwidth on an optical fiber. DWDM operates by multiplexing and transmitting a number of signals, i.e. OC-48/STM-16, OC-192/STM-64, or OC-768/STM-256, simultaneously at different wavelengths on the same optical fiber. As a result, a single optical fiber provides a number of virtual optical fibers by carrying a number of simultaneous signals. This permits greater network traffic through increased bandwidth.
The most aggressive service providers have deployed 40 channel DWDM systems with transmission distances limited to around 500 km before requiring Optical-Electrical-Optical (O-E-O) regeneration of the optical bit streams. Thus, DWDM systems are connected back-to-back for cross country connectivity. In order to overcome these limitations, DWDM system manufacturers are presently offering to at least double both channel count and transmission distance. More elaborate technologies will lead to greater length (x) bandwidth products and true ultra-long haul systems.
Along with the interests aimed at increasing both transmission length and bandwidth, a greater importance is being placed on developing more efficient network management tools and test equipment. Service providers have been instrumental in driving this development and embedding performance measures and diagnostic tools into their system elements. Circuit tests that are performed by field technicians include, for example, tests for optical power levels, loss of signal modulation, and code violations.
Currently, field technicians cannot trouble-shoot an entire cross country DWDM circuit without tremendous group coordination. Each cross country DWDM circuit comprises a number of sub-circuits that must be administered by a local field technician during a test. For example, a circuit from State 1, which is located in one region of a country, to State 4, which is located in a distant region of the country, might comprise multiple, sequential sub-circuits from State 1 to State 2, State 2 to State 3, and State 3 to State 4. During a test, a local field technician for a sub-circuit can only monitor and trouble-shoot their individual sub-circuit. Therefore, to obtain information relating to another sub-circuit, a field technician must either communicate with another field technician who is monitoring the other sub-circuit or rely on personnel in a Network Operation Center (NOC) that can survey the entire circuit.
Less reliance on the NOC is desired. It is impractical for a NOC to be heavily involved in turn-up testing or prolonged maintenance tasks. A NOC should rather be focused on in-service traffic management.
Currently, field technicians test circuits with a device that has both a transmitter for transmitting a test-drive signal on a circuit and a receiver for receiving the test-drive signal after it is returned from a far end of the circuit. The transmitter/receiver couples to a near end of the circuit at, for example, a fiber access panel. A variety of tests are routinely performed via the transmitter/receiver unit that include tests for optical power levels, loss of signal modulation, and code violations. Much of the time of circuit testing is spent, based on actual field experience, in performing continuity tests on turn-up testing before final Bit Error Ratio (BER) testing. This may be easily handled by keying in a number of B1 byte errors and confirming counters correctly incremented downstream; some technicians may use simple on/off laser control and look for Loss of Signal (LOS) and Loss of Frame (LOF) at downstream system ingress and egress points. Lacking continuity may require an installations technician to be dispatched to trouble-shoot and complete a cross-connect.
Each of these tests requires careful attention to detail. Since the transmitter/receiver and the fiber access panel are typically of an open-chassis design, they provide a potential electrical shock hazard to the field technician, who manipulates pushbutton operators located directly on the transmitter/receiver. Also, the field technician is limited to working proximate to the transmitter/receiver in order to operate the device. This disadvantageously limits the field technician's zone of movement during testing.
It is therefore desirable to empower field operations by providing the tools and test equipment to efficiently manage turn-up and maintenance requirements.